Whey salt powder, process for its production and its use

ABSTRACT

The invention relates to a whey salt product, which is not bitter in taste, and which is characterized by containing 19 to 27% potassium, 0.5 to 2% calcium, 5 to 7% sodium, 0.1 to 1% magnesium, 17 to 37% chloride and 0.5 to 3 % phosphorus and further 10 to 20% protein and 10 to 35% lactose, to a process for its production and its use as a table salt substitute. According to the invention, the whey salt powder is prepared in such a way that whey or an ultrafiltration. permeate with a dry matter content of 20% by weight at the most, obtained from milk or whey, is filtered through membranes by using nanofiltration membranes, the permeate with a dry matter content of 0.1 to 1.0% by weight obtained from nanofiltration is concentrated and finally dried to powder.

The invention relates to a whey salt powder, which is not bitter intaste, a process for its production, and its use. The whey salt powderin accordance with the invention is a product containing naturalminerals of whey and it may replace totally or partly the conventionalsalt used in food and food products.

In the production of cheese, when taste-softening casein and fat areprecipitated from milk into a cheese mass, what remains is whey with asalty taste. The salty taste of whey restricts its use in food industry.To reduce the salt content in whey, various methods have been developed,such as electrodialysis, ion exchange, and most recently nanofiltration.In fact, nanofiltration is a concentration process based on reverseosmosis, in which membranes used are so coarse that, in addition towater, particularly monovalent ions permeate the membrane. It is wellsuited for pre-concentration of dilute solutions, such as whey, from adry matter content of 6% to 24% at the most. In the present publication,percentages refer to percentages by weight, unless otherwise indicated.

With the above desalination processes and combinations thereof isproduced demineralized whey powder, which is generally used e.g. in babyfoods, chocolate and ice cream. For instance in Finland, the major partof whey is used for producing demineralized whey powder. In theseprocesses, the removed salts pass through wastewater treatment plantsinto water systems.

Another common whey processing method is ultrafiltration. In thisprocess whey proteins are concentrated by means of a membrane system,which retains macromolecular components of whey. The concentrate isdried to whey protein powder, which is commonly used in food industry,for instance as a milk powder substitute. Also milk can be ultrafilteredsimilarly.

In the ultrafiltration of both whey and milk, a permeate passing throughthe membrane contains the lactose and salts as well as othermicromolecular substances. The ultrafiltration permeate is commonly usedfor producing lactose by crystallization. The residual permeate motherliquid tastes very salty and it is extremely difficult to dry, so it iscommonly sold at a very low price as a liquid concentrate for animalfeed.

Currently, the whey salts have generally a negative value only and theyend up in waste water or animal feeding, even though the quantities usedare restricted even in animal feeding. Thus there is a constant need tofind ways how the salts in whey can be put to good use.

The mineral composition of whey is highly physiological, since it is thesame as that of blood serum. It contains valuable minerals: potassium,calcium and magnesium, and its sodium content is rather low. Table 1shows the mineral composition of whey calculated in percentages byweight of dry matter.

TABLE 1 Mineral composition of whey (% of dry matter) minerals 8.8calcium 0.9 sodium 0.8 potassium 2.2 magnesium 0.1 phosphorus 0.7chloride 2.0 citrate 2.5 lactate 1.5

The high potassium content of whey protects a human organism fromadverse effects of sodium. Magnesium in turn prevents hypertension. Asanions, whey contains phosphate, citrate and lactate in addition tochloride. If the salts in whey could be separated and prepared into adry product, a natural, mineral-salt-like preparation would be achieved.

Mineral salts substituting table salt (NaCl), prepared by mixing variouschemicals, have been disclosed (European Patent 124 254; German Patent31 07 800). However, these are not natural mineral salt preparations.

European Patent Applications 408 756 and 291 980 disclose use of apermeate mother liquid, an inconvenient by-product of lactoseprocessing, as a salt substitute. The permeate mother liquid, thecomposition of which is presented in Table 2, contains mainly lactose,however, so it is not suitable for a mineral salt as such.

TABLE 2 Composition of permeate mother liquid (% of dry matter) lactose56 protein 15 minerals 22

It is also almost impossible to dry the permeate mother liquid due toits high hygroscopicity.

Attempts have been made to remove salts from the permeate mother liquidby nanofiltration and to crystallize the obtained salt solution intosome kind of whey salt. European Patent Application 536 612 discloses aprocess for removing salts from a salty permeate mother liquid bynanofiltration, whereafter the permeate from nanofiltration isevaporated and from the residue is crystallized mainly potassiumchloride, in which some of other components of the permeate remain asimpurities. The composition of the obtained salt product is presented inTable 2 on page 5 of said European Patent publication.

The process in accordance with European Patent Application 536 612 isimpractical, since therein nanofiltration is needed as an extra processstep which is used for desalination only. However, nanofiltration doesnot suit well for treating concentrated solutions, since processpressure must exceed the osmotic pressure of the solution in order tomake water flow in the osmotically ‘wrong’ direction. Further problemswith said known process are poor crystallization yield, difficultafter-treatment of crystal mass, and residual liquid from potassiumchloride crystallization, for which no application has been set forth.

Surprisingly, we have now been able to produce a whey salt powder, whichis a natural, mineral-salt-like preparation and which can be used as atable salt substitute. This whey salt powder is not bitter in taste.

The whey salt powder in accordance with the invention is characterizedby containing

potassium 19-27% calcium 0.5-2%   sodium 5-7% magnesium 0.1-1%  chloride 17-37% phosphorus 0.5-3%   and further protein 10-20% lactose10-35%

The novel whey salt powder developed by us has a saltier taste than thesalt preparation disclosed in Finnish Patent 98696, so to achieve thesame salty taste, new whey salt powder is needed in much smallerquantities than said known salt preparation. The whey salt powder inaccordance with the invention is not, however, bitter in taste, eventhough its potassium content is higher than that of the salt preparationdisclosed in Finnish Patent 98696, but not so high as in the saltpreparation disclosed in European Patent Application 536 612.Excessively high potassium content is known to make salt bitter intaste.

In the whey salt powder in accordance with the invention, proteins andlactose are present to cover bitterness. Our experiments proved that anaqueous solution prepared from the whey salt powder in accordance withthe invention is not bitter, but both an aqueous solution prepared frommere potassium chloride, equal in potassium content, and an aqueoussolution of whey salt prepared with the process in accordance withEuropean Patent Application 536 612 are bitter in taste, as it appearsfrom examples 6 and 7 here below.

The composition of the whey salt powder disclosed in Table 2 on page 5of European Patent Application 536 612 substantially differs from thewhey salt powder of the invention defined in claim 1, since the knownwhey salt powder is mainly ash (83.5%) being composed of bitterpotassium (42%) and chloride (38%). This results from the productionprocess of the known whey salt powder, in which the potassium chlorideis crystallized from a concentrated nanofiltration permeate. Because ofthe high potassium chloride content said known whey salt is clearlybitterer and worse in taste than the new whey salt powder of theinvention which is prepared by the process disclosed in the presentpatent application.

Since the whey salt powder of the invention and the solution madetherefrom are not bitter, particularly as compared with a salt solutionwith equal potassium content, they are excellent substitutes for tablesalt and other salt preparations both in industry and in a variety ofcooking facilities.

An advantageous whey salt powder of the invention contains

potassium 25-26% calcium 0.8-2%   sodium 5-6% magnesium 0.1-0.2%chloride 32-37% phosphorus 1.4-3%   and further protein 10-20% lactose10-35%

The whey salt powder contains protein most preferably 10 to 16% andlactose most preferably 10 to 15%.

The most advantageous whey salt powder of the invention is the whey saltpowder of. Example 1, whose composition of the main components ispresented in Table 3 below.

At the same time, we have unexpectedly discovered a new process forproducing whey salt powder, whereby whey salt powder can be producedeconomically, easily and with a good yield. In accordance with theinvention, whey salt powder is obtained, when whey or whey permeate isappropriately treated with membrane filtration, whereby lactose andproteins are removed, whereafter the obtained permeate is dried topowder.

The new process for producing whey salt powder in accordance with theinvention is characterized in that whey or ultrafiltration permeateobtained from milk or whey, whose dry matter content is at most 20% byweight,

is filtered with membrane by using nanofiltration membranes,

the permeate with a dry matter content of 0.1 to 1.0% by weight,obtained through nanofiltration, is concentrated and

finally it is dried to powder.

As stated in the above specification, nanofiltration does not suit wellfor treating concentrated solutions. However, in the process of theinvention, nanofiltration is utilized to the full, in the respect thatit is used here as a concentration process to replace evaporation, andsimultaneously, some of the salts are removed, which improves the usevalue of whey concentrate. On the other hand, the whey powder of theinvention contains all whey components that have passed through thenanofiltration membrane. Thanks to the process of the invention, all thedry matter in whey can thus be utilized. By using the process of theinvention, more whey salt is recovered than previously, and at the sametime, wastewater problems caused by whey are avoided, since there willbe no waste water at all.

In the new method of the invention, starting material can be whey, suchas cheese whey, casein whey or curd whey, or a permeate obtained frommilk or whey by ultrafiltration, the dry matter content of the whey orpermeate being at most 20% by weight, suitably at most 15% by weight andpreferably 5 to 10% by weight. If necessary, prior to nanofiltration thedry matter content of the whey or permeate used as the starting materialis adjusted to any one of the above values.

Nanofiltration employs semi-permeable membranes, which are preferably150 to 300 Da membranes. Suitable are, for instance, Desal-5 DKmembranes, manufactured by Osmonics, USA, or Dow NF45 membranes,manufactured by Dow, USA.

A permeate obtained through nanofiltering whey or ultrafiltrationpermeate is a dilute salt solution with a dry matter content of 0.1 to1.0% by weight, preferably 0.3 to 0.5% by weight. This permeate can beconcentrated either by evaporation or by a combination of reverseosmosis and evaporation suitably to a dry matter content of 30 to 40% byweight, preferably to a dry matter content of 35 to 40% by weight. Insaid reverse osmosis, by which the permeate is first suitablyconcentrated to a dry matter content of 4 to 24% by weight, reverseosmosis equipment having membranes with 99% Cl-ion rejection can besuitably used. Suitable membranes are, for instance, TFC® 2822HR-NW typemembranes manufactured by Fluid Systems, USA.

We found unexpectedly that the above-described whey salt concentrate canbe readily spray-dried with a conventional drier used for drying milkpowder and whey powder, even though both lactose and salts areconsidered extremely hygroscopic and difficult to dry. The specificweight of dry powder thus obtained is about 0.4 to 0.6 g/ml and itsmoisture content is about 2%.

Obviously, micromolecular nitrogen compounds passing through thenanofiltration membrane act as a carrier in the product and, on theother hand, the most hygroscopic salts do not pass the nanofiltrationmembrane.

Undoubtedly, fear of steel corrosion in the equipment, when operating inhigh chloride contents, has impeded utilization of whey salts. However,in our experiments we did not find corrosion in the equipment, norraised iron content in the whey salt powder.

In the above-described manner, whey salt powder can be produced simplyand with good yield from the salt solution which currently burdenswastewater treatment plants, the whey salt powder being a naturalmineral salt preparation and a table salt substitute both in industryand in households, with which the table salt can be replaced totally orpartly in food and food products.

In the following examples the invention is described in greater detail.

EXAMPLE 1

Cheese whey with a dry matter content of 6.5% was used as a rawmaterial. The whey contained 73% lactose, 12% protein and 8% ash of thedry matter. The whey was separated and sieved, whereafter it waspasteurized and nanofiltered through semi-permeable membranes (150-300Da; Desal-5 DK). Of the whey salts mainly the salts composed ofmonovalent ions (sodium, potassium, chloride) were removed together withwater through the membranes into the permeate. The removal into thepermeate comprised-50% of the salts and 1% of the lactose.

In filtering the whey, dry matter content of the retentate was 22%. Withthe equipment used, the feed flow rate was 25,000 l/h, the flow rate ofthe retentate was 5,000 l/h and the flow rate of the permeate 20,000l/h. The filtering temperature was 20° C. and the process pressure was22 bar.

The nanofiltration permeate (dry matter content 0.4%) was furtherconcentrated with reverse osmosis equipment having membranes with 99%Cl-ion rejection. The membranes were of type TFC® 2822HR-NW. Retentatewith a dry matter content of 4% was thus obtained, and the permeatecould be reused as industrial process water.

The obtained reverse osmosis concentrate was concentrated by evaporationto a dry matter content of 40% and dried to powder with a conventionalspray drier.

The amounts, in percentages by weight of the total composition, of themain ingredients of the obtained whey salt powder are presented in Table3.

TABLE 3 Main ingredients of whey salt powders Cheese Curd Casein MilkWhey whey whey whey permeate permeate (example (example (example(example (example 1) 3) 2) 4) 5) Potassium 26% 26% 25% 26% 26% Calcium0.9%   2%  2% 0.8%  0.8%  Sodium  6%  5%  5%  6%  6% Magnesium 0.1% 0.1%  0.1%  0.1%  0.1%  Chloride 32% 33% 37% 32% 33% Phosphorus 1.5%  3%  3% 1.5%  1.4%  Protein 15% 15% 15% 14% 14% Lactose 13% 13% 12%14.5%   15%

EXAMPLE 2

Raw material was casein whey whose dry matter content was 5.6%. The wheycontained 70% lactose, 16% protein and 14% ash of the dry matter. Thewhey was seperated and sieved, and it was pasteurized and nanofilteredin accordance with Example 1. The permeate from nanofiltration wasconcentrated by reverse osmosis and the concentrate was evaporated anddried to powder in accordance with Example 1.

The composition of the main ingredients in the obtained whey salt powderis presented in Table 3.

EXAMPLE 3

Raw material was curd whey whose dry matter content was 5.7%. The curdwhey contained 68% lactose, 8% protein and 9% ash of the dry matter. Theseperated and sieved whey was pasteurized and nanofiltered in accordancewith Example 1. The permeate from nanofiltration was concentrated byreverse osmosis and the concentrate was evaporated and dried to powderin accordance with Example 1.

The composition of the main ingredients in the obtained whey salt powderis presented in Table 3.

EXAMPLE 4

Raw material was a permeate with a dry matter content was 6%, obtainedby ultrafiltration from fat-free milk. The permeate contained 83%lactose, 5% protein and 9% ash of the dry matter. The permeate waspasteurized and nanofiltrated in accordance with Example 1. The permeatefrom nanofiltration was concentrated by reverse osmosis and theconcentrate was evaporated and dried to powder in accordance withExample 1.

The composition of the main ingredients in the obtained whey salt powderis presented in Table 3.

EXAMPLE 5

Raw material was a permeate with a dry matter content of 10%, obtainedby ultrafiltration from whey. The whey permeate contained 83% lactose,5% protein and 8% ash of the dry matter. The permeate was pasteurizedand nanofiltrated in accordance with Example 1. The permeate fromnanofiltration was concentrated by reverse osmosis and the concentratewas evaporated and dried to powder in accordance with Example 1.

The composition of the main ingredients in the obtained whey salt powderis presented in Table 3.

EXAMPLE 6

Aqueous solutions with equal potassium content (1.9 g/l) were preparedfrom the whey salt powder of the invention made from cheese whey andfrom potassium chloride (KCl). In sensory evaluation, ten persons testedthe solutions and evaluated their bitterness on the scale from 1 to 10.A T-test was conducted on the material. The average bitterness of thepotassium chloride solution was 6.87 and that of the whey salt solution1.74. The difference in bitterness is statistically significant(p=0.000089).

EXAMPLE 7

Whey salt was prepared in accordance with the method disclosed inEuropean Patent Application EP-A1-0 536 612 and the obtained knownproduct was compared in sensory evaluation with the whey salt powder ofthe present invention made from cheese whey. There were eight evaluatorsand the evaluation scale ranged from 0 to 10. The evaluators wererequested to evaluate the taste of the 1% solutions in view of theirbitterness and pleasantness. The bitterness of the above-mentioned knownwhey salt was 5.72 and the pleasantness 2.67. The bitterness of the wheysalt of present invention was only 2.1 and the pleasantness of taste was6.22. The difference in bitterness was statistically significant(p=0.0074).

We claim:
 1. A whey salt powder comprising, in weight %: potassium19-27% calcium 0.5-2%   sodium 5-7% magnesium 0.1-1%   chloride 17-37%phosphorus 0.5-3%   protein 10-20% lactose  10-35%.


2. A whey salt powder as claimed in claim 1, comprising, in weight %:potassium 25-26% calcium 0.8-2%   sodium 5-6% magnesium 0.1-0.2%chloride 32-37% phosphorus 1.4-3%   protein 10-16% lactose  10-15%.


3. A process for producing the whey salt powder as claimed in claim 1,comprising filtering a whey or an ultrafiltration permeate whose drymatter content is at most 20% by weight obtained from a startingmaterial comprising milk or whey with nanofiltration membranes to obtaina permeate with a dry matter content of 0.1 to 1.0% by weight,concentrating the permeate, and drying the concentrate to a powder. 4.The process as claimed in claim 3, wherein the starting material iswhey, the dry matter content of the whey being at most 15% by weight. 5.The process as claimed in claim 3, wherein prior to nanofiltration withmembranes the dry matter content of the whey or the permeate obtainedfrom milk or whey is adjusted to a value which is at most 20% by weight.6. The process as claimed in claim 3, wherein nanofiltration membranesof 150-300 Da are used in nano-filtration.
 7. The process as claimed inclaim 6, wherein the permeate obtained from nanofiltration isconcentrated by evaporation to a dry matter content of 30 to 40% byweight.
 8. The process as claimed in claim 6, wherein the permeateobtained from nanofiltration is concentrated first with reverse osmosisequipment having membranes with 99% Cl-ion rejection, to a dry mattercontent of 4 to 24% by weight, and thereafter by evaporation to a drymatter content of 30 to 40% by weight.
 9. The process as claimed inclaim 3, wherein the concentrated nanofiltration permeate is dried topowder by spray drying.
 10. A method of using a whey salt powdercomprising at least partially substituting the whey salt powder of claim1 for conventional salt in food and food products.
 11. The process ofclaim 4, wherein the starting material comprises at least one of cheesewhey, casein whey, curd whey or permeate obtained by ultrafiltration ofmilk or whey, the dry matter content of the starting material is at most15% by weight.
 12. The process of claim 5, wherein the dry mattercontent is at most 15% by weight.
 13. The process of claim 5, whereinthe dry matter content is at most 10% by weight.